Covulcanizable rubber composition

ABSTRACT

A COVULCANIZABLE COMPOSITION WHICH COMPRISES A MIXTURE OF 5-95% BY WEIGHT OF BUTADIENE-ACRYLONITRILE COPOLYMER RUBBER AND 95-5% BY WEIGHT OF EPICHLOROHYDRIN POLYMER RUBBER, AND A VULCANIZATION AGENT CONSISTING OF, PER 100 PARTS BY WEIGHT OF THE FIRST MIXTURE, (I) 0.5-5.0 PARTS BY WEIGHT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF AROMATIC POLYAMINES, THEIR SALTS, ALIPHATIC POLYAMINES, THEIR SALTS, CYCLOALIPHATIC POLYAMINES, 2-MERCAPTOIMIDAZOLINE, 2-MERCAPTOPYRIMIDIN, THIOUREA AND SUBSTITUTED THIOUREA, (II) 1.0-10.0 PARTS BY WEIGHT OF AN OXIDE, AROMATIC CARBOXYLATE, ALIPHATIC CARBOXYLATE OR PHOSPHATE OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, CALCIUM, ZINC, CADMIUM, LEAD AND TIN, AND (III) 0.3-3.0 PARTS BY WEIGHT OF AN ORGANIC PEROXIDE.

United States Patent 3,639,651 COVULCANIZABLE RUBBER COMPOSITION Keiji Komuro, Tokyo, Masaaki Inagami, Kohoku-ku, Yokohama, and Yoshiomi Saito, Kanagawa-ken, Japan, 1ssignors to The Japanese Geon Company, Ltd., Tokyo,

a an N3 Drawing. Filed Mar. 4, 1969, Ser. No. 804,274 Claims priority, application Japan, Mar. 9, 1968, 43 4,956 Int. Cl. C08d 9/08 US. Cl. 260-23.7 M 3 Claims ABSTRACT OF THE DISCLOSURE A covulcanizable composition which comprises a mixture of 95% by weight of butadiene-acrylonitrile copolymer rubber and 95-5% by weight of epichlorohydrin polymer rubber, and a vulcanization agent consisting of, per 100 parts by weight of the first mixture, (I) 0.5-5.0 parts by weight of a member selected from the group consisting of aromatic polyamines, their salts, aliphatic polyamines, their salts, cycloaliphatic polyamines, Z-mercaptoimidazoline, 2 mercaptopyrimidin, thiourea and substituted thiourea, (II) 1.0l0.0 parts by weight of an oxide, aromatic carboxylate, aliphatic carboxylate or phosphate of a metal selected from the group consisting of magnesium, calcium, zinc, cadmium, lead and tin, and (III) 0.3-3.0 parts by weight of an organic peroxide.

This invention relates to a covulcanizable rubber composition comprising a butadiene-acrylonitrile copolymer rubber and an epichlorohydrin polymer rubber.

Conventionally, rubbers of difierent types have been blended in various purposes, to provide various rubber compositions. In such blending, however, normally the properties of a resulting composition approach to those of the inferior component among the constituents employed. This phenomenon is particularly remarkable in respect of strength characteristics, which obviously is objectionable. This tendency is more conspicuous in cases of blending rubbers of dilferent vulcanization systems. Thus, blended compositions of butadiene-acrylonitrile copolymer rubber and epichlorohydrin polymer rubber are also subject to this drawback.

Butadiene-acrylonitrile copolymer rubber (hereinafter will be abbreviated as NBR) exhibits excellent oil resistance and heat stability, and has been used for many years as oil-resistant and heat-stable rubber, particularly in the field of industrial parts. The same rubber, however, shows an inferior weatherability and ozone resistance. Therefore, it is desirable to impart still better oiland heat-resistant properties to the rubber, as well as to improve its weatherability and ozone resistance.

Whereas, epichlorohydrin polymer rubber (hereinafter will be abbreviated as OHR) exhibits superior oil resistance, heat stability, Weatherability, and ozone resistance to those of NBR, but is inferior in strength properties.

Accordingly, it was expected that when NBR and CH-R are blended, a rubber composition of favorable properties would be obtained by the components mutual compensation of respective shortcoming. However, since NBR and C'HR are of entirely different vulcanization systems, compositions of only unsatisfactory properties are obtained due to non-uniform vulcanization, when known vulcanization agents are employed. Then US. Pat. No. 3,351,517 proposes one method of covulcanizing epichlorohydrin copolymer and sulfur-vulcanizable rubber, in which the vulcanization agent comprises (1) an organic vulcanization accelerator such as Z-mercaptoimidazoline, 2-mer- "ice captopyrimidin, or thiourea, (2) a salt or oxide of a metal belonging to IIA, II-B, III-A, IVA, or V-A Group of Periodic Table, and (3) sulfur. However, so obtained covulcanized product exhibits unsatisfactory strength properties such as tensile strength and abrasion resistance, and furthermore markedly inferior elasticity.

Accordingly, therefore, the object of the invention is to provide compositions of excellent heatand oil-resistances, and improved strength properties, weatherability, ozone resistance and elasticity, by blending of NBR and CHR.

The above object of the invention is accomplished by the use of a vulcanization agent consisting of (I) a member of the group consisting of aromatic polyamines, salts thereof, aliphatic polyamines, salts thereof, cycloaliphatic polyamines, Z-mercaptoimidazoline, 2-mercaptopyrimidin, thiourea and substituted thiourea,

(II) an oxide, aromatic carboxylate, aliphatic carboxy late, or phosphate of a metal selected from the group consisting of magnesium, calcium, zinc, cadmium, lead and tin, and

(III) an organic peroxide for covulcanization of NBR and CHR.

The precise mechanism with which the foregoing excellent result is obtained is not yet clear. However, in accordance with the invention, it is possible to assimilate the vulcanization progressing conditions of NBR and CHR. Accordingly an even or uniform vulcanization of the blended composition can be expected, and in certain cases cross-linkage advances between NBR and CHR.

The blending ratio of NBR and CHR in the compositions of the invention can be optionally varied within the ranges of 5-95 wt. percent of NBR and -5 wt. percent of CHR, while the desired effects of the invention are achieved most conspicuously at the ratios of 20-80 wt. percent of NBR to 80-20 wt. percent of CHR. Individual blending ratio should be determined in accordance with the specific utility to be obtained. For instance, it is recommended to use at least 20 wt. percent of CHR for improving ozone resistance of 'NLBR, and also at least 30 wt. percent of the former for improving the heat and oil resistances of the latter. Likewise, at least 15 wt. percent of NBR should be used to improve strength properties, compression set, and Williams abrasion of CHR.

The vulcanization system of the invention is composed of the above-described three components in combination. Examples of the first component (I) include paraphenylenediamine, naphthalenediamine, ethylenediamine, hexamethylenediamine, salts of those polyamines, melamine, piperazine, Z-mercaptoimidazoline, Z-mercaptopyriinidine, thiourea, ethylenethiourea, trimethylthiourea, diethylthiourea and dibutylthiourea. Examples of the second component (H) include oxides of magnesium, calcium, zinc, cadmium, lead and tin; magnesium benzoate, calcium benzoate, lead oleate, lead phthalate, and magnesium phosphate. Among the named metallic compounds, those of lead, magnesium and zinc give the most favorable results. All of the above-named first and sebond components are known as vulcanization agents of CHR, and presumably function mainly as such agents for CHR also in the blended compositions of the invention: Examples of the third component (HI) include benzoyl peroxide, tertiary butyl hydroperoxide, ditertiary butyl peroxide, dicumyl peroxide, dichloro-dibenzoyl peroxide, etc.

In order to accomplish the object of this invention, normally 0.5-5.0 Wt. parts of the first component, 1.'O 10.0 wt. parts of the second component, and 0.3-3.0 wt. parts of the third component, are added to wt. parts of a NBR-CI'IIR mixture. Since the components do not affect each other in the described vulcanization system of the invention, a stable blended composition can be obtained. The respective amount of the three vulcanization agents should be determined in accordance with the blending ratio of NBR and CHR, so that the vulcanization rates of the rubbers should become equal if all possible. For example, if the correlation of the addition amount of mixture of the first component (amines) and second component (metallic compounds) versus vulcanization rate of CHR, and the correlation of addition amount of the third component (organic peroxides) versus vulcanization rate of NBR are empirically determined in advance, the respective amounts of the three components required in correspondence to any specific blending ratio of NBR and CHR can be easily calculated.

The NBR employed in the invention includes all butadieneacrylonitrile copolymer rubbers obtained by conventional emulsion or solution polymerization, so far as their Mooney viscosities ML (100 C.), are within the range of 30-130, regardless of their acrylonitrile contents. Also as useful CHR, epichlorohydrin homopolymer rubber and copolymer rubbers of epichlorohydrin with olefin oxides such as ethylene and propylene oxides may be named. Any of such epichlorohydrin-containing butadiene-acrylonitrile copolymer containing 32-35 Wt. percent of acrylonitrile, having a Mooney viscosity, ML (100 C.), of 70. The CHR was an epichlorohydrin homopolymer having a Mooney viscosity, ML (100 C.), of 67. (Unless otherwise specified, the identical NBR and CHR were used in all of the following examples and controls.) Also for comparison, NBR alone and CHR alone were similarly milled and vulcanized in Controls 1 and 2.

TABLE 1 Example Control Control Composition 1 1 2 2 NB R 100 75 50 CHR c 25 75 100 Carbon black N550. 30 30 30 30 30 Zinc stearate 0. 25 0. 5 0. 75 1.0 ed lead 1. 25 2. 5 3. 75 5.0

Hexamethylene carbamate 0. 5 l. 0 1. 5 2. 0 Dieumyl peroxide" 1. 13 0. 75 0. 37

The physical properties of the vulcanized products were as given in Table 2.

TABLE 2 Example Control Control Physical property 1 1 2 3 2 Tensile strength (kg/cm?) 201 198 196 178 169 Elongation (percent) 490 530 560 480 320 100% modulus (kg./crn. 22 22 21 29 44 Hardness (I IS) 61-55 -53 55-49 57-51 -63 Compression set, C. 70 hrs. (percent) 18. 2 25. 1 29. 1 33. 5 53. 0 Williams abrasion (ec./HP- hr.) 2 690 640 450 620 910 Air test tube, aged 6 days at 0.:

Change in tensile strength (percent) -74. 2 -39. 9 27. 0 17. 4 -15. 7 Change in elongation (percent)..; -81. 7 66.0 -59. 0 -52. 2 -33. 4 Change in. hardness +9-+l1 +8-+9 +9-+0 +9-+8 +10-+7 Air test tube, aged 3 days at 0.:

Change in tensile strength (percent) -65. 3 -80. 0 Change in elongation (percent) -66. 8 +22. 2 Change in hardness +3-l -13--18 ASTM #3 oil, aged 70 hrs. at 100 Change in tensile strength (percent) -28. 3 -21. 7 -19. 1 -10. 7 11. 8 Change in elongation (percent) -16. 3 -18. 8 10. 7 10. 4 -19. 3 Change in 100% modulus (percent) -27. 3 -22. 7 -19. 0 20. 7 2. 4 Change in hardness -13--9 -12--9 11--7 -9--6 -7--7 Change in volume (percent) +19. 9 +19. 2 +13. 6 +12. 2 +9 Ozone resistance, 100 p.p.m., 30 C., 20% elongation: Number of hours passed before first crack 4 appeared 2 17 136 320 1 Measured with products of C., 45 minutes vulcanization, according to ASTM D-395-61. 2 Measured in accordance with ASTM D-394-59.

3 No crack observed.

polymer rubber can be used in this invention, so far as its Mooney viscosity, ML (100 C.), is within the 5 EXAMPLES 1-3 AND CONTROLS l-2 Compositions were prepared at the blending ratios specified in Table l, which were subsequently milled with an open roll for 30 minutes at 50-80 C., and vulcanized for 30 minutes at 155 C. The NBR employed was a EXAMPLES 4-6 AND CONTROLS 3-4 Compositions were prepared at the blending ratios indicated in Table 3 below, and milled with an open roll for 30 minutes at 50-80 C., followed by 30 minutes vulcanization at 155 C. Also for comparison, cases of similarly milling and vulcanizing NBR or CHR alone are also given as Controls 3 and 4. Note that Control 3 is identical with Control 1, which is given simply for convenient comparison.

TABLE 3 Example Control Control Composition 3 4 5 4 75 50 25 25 50 75 100 80 30 30 80 Zine stearate 0. 25 0. 5 0. 75 1. 0 Red lead 1. 25 2. 5 3. 75 5.0 2-mercaptoimidazolino. 75 1. 5 2. 25 3. 0 Dicumyl peroxide 1. 5 1.12 0. 75 0. 37

The physical properties of the resulting vulcanization products are given in Table 4.

' TABLE 4 Example Control Conlrol Physical property 3 4 5 6 4 'lensile strength (kg/cm?) 204 209 194 181 145 h ong tion (percent) 4110 570 500 450 330 100% modulus (kg/cm. 2 22 24 30 42 H srdness (11S) 61-65 157-61 67-52 59-54 65-63 Compression set, 100 C.X7O hrs. (puree-n1) l8. 2 27.0 38. 43.0 49. 6 Wil iams abrasion (ccJHP- hr.) 690 670 1370 760 810 Air test tube, aged 6 days 111.130 0.:

Change in tensile strength (percent) 74. 2 -19. 2 -,-41. 8 -2l. 1 -6. 9 Change in elongation (percent) 7 S1. -73. 6 -72. 0 64. 54.6 Change in hardness +9-+11 +9-+13 +11-+12 +11-+12 +-+10 Air test tube, aged 3 days at 150 C.:

7 Change in tensile strength (percent) -71.8.v -70.9 -77.5 63. 5 1l.7

Change in olon etion (porcont) 73.0 8G.0 86.0 --80.0 36. 4 v Change in her ness +13-+16 +l)/-+1b +13-+l3 +7-+7 +3-+l AB'IM #3 oil, aged 70 hrs. et100 C.:

' Change in tensile strength- 23. 9 3-1. 1 2il. 3 -23. 4 Change in elon etion Sporcen 22.8 --42.0 46.7 -46.5 Change in 1007.: modu us (perce -13.0 +16. 7 +26. 6 +38. 1 Change in hardness; 1l--7 5--3 -3-0 1-1 Chen evin volume (perccnt) +19. 4 +111 +10. 3 +11. 2

Ozone res tance, 100 p.p.m., o I

tion: Number oi hours passed before first crack appeared 2 36 270 320 Measurcd with products of 165 C., minutes vulcanization, according to ASTM D-3J5-61.

Measured in accordance with ASTM D-(iJ-i-bil. No crack observed.

EXAMPLES 7-13 Compositions were prepared at the blending ratios indicated in Table 5 below, and milled with an open 7. 30 rninutes at -80 C. followed by 30 minutes vulcanroll for ization at 155C.

TABLE 15 Example. 7

Composition:

. llomrnethylone dlemine carbnmem. 2-rnercuplobcnzirnidazoline llutadieno ucrylonitrlle (40) oopolymer llutadiene (no), enrylonltrile (84) copolyrner I liutudiene (71), ncrylonitrile (2i copolyrner I Eplchlorohfydrln hmnopolymer 4 Eplchlorohydrin (es), ethylene oxide (82) lymer Dicurnyl peroxide t-Butyl pcrbenzoate l Mooney viscosity 78.

1 Mooney viscosity 80. Mooney viscosity 76. 4 Mooney viscosity 70.

5 Mooney viscosity 81.

The physical properties of the vulcanized products were as given in Table 6. V

TABLE 6 Example 7 8 e 10 11 12 13 Physical ropcrty:

Tens estrength (kg./crn.).... 212 102 190 170 181 180 184 Elongation (percent) 610 600 650 480 660 370 610 modulus (kg/cm!) 20 22 17 21 16 39 24 lid -60 b6-50 515-49 W 63--18 00-67 67-62 I1 nrdncss (JIS) 7 CONTROLS -9 Compositions were prepared at the blending ratios given 111 Table 7, and milled with an open roll for 30 minutes at (3., followed by 30 minutes vulcanization at The physical properties of the resulting vulcanized products are given in Table 8.

hydrin polymer rubber, said composition containing a vulcanization agent consisting of, per 100 parts by weight of said mixture of rubbers, (I) 0.5-5.0 parts by weight of a member selected from the group consisting of aromatic polyamincs, salts of said aromatic polyamines, aliphatic polyamines, salts of said aliphatic polyamines, cycloaliphatic polyamines, 2 mercaptoimidazoline, 2- mercaptopyrimidin, thiourea and substituted thiourea, (11) 10-100 parts by weight of an oxide, aromatic carboxylate, aliphatic carboxylate or phosphate of a metal selected from the group consisting of magnesium, calcium, zinc, cadmium, lead and tin, and (III) 0.3-3.0 parts by weight of an organic peroxide.

2. The covulcanizable composition 01' claim 1 wherein said composition comprises a mixture of -80% by weight of said butadiene-acrylonitrile copolymer rubber and 80-20% by weight of said epichlorohydrin polymer rubber.

TABLE 8 3 Control 6 6 7 B 9 Physical property:

TettSi 0 Strength (kgJcmfi) 216 174 167 157 146 Elongation (percent) 380 370 3'20 320 330 100% modulus (kgJemJ) 1.3 3t 38 38 Hardness (J18) 00-68 00-68 62-60 Compression set, 100C.X70 hrs. (percent)'.. 47.3 40. 2 34.9 40. 5 65. 0 Williams abrasion (cc-IHP- hr.) 670 790 940 900 1,010 Air test tube, aged 6 days at 130C:

Change in tensile strength b0. 0 -7.6 28.7 11.8 12. 2 Change in elongation (percent) -75. 8 69. 4 --68. 7 -68. 2 -66.8 Change in hardness +12-+11 +16-+15 +13-+13 +13-+13 +14-+14 Air test tube, aged 3 days at 150C.:

Change in tensile strength (percent) -62. 7 -3l. 0 -40. 7 -20. 9 -13. 0 Change in elongation (percent) -86. 76. 7 -75.0 69. 8 -68. 8 Change in hardness +1l-+9 +16-+16 +14-+14 +14-+13 +9-+11 ASTM #3 011, aged 70 hrs. at 100 Change in tensile strength. -8. 3 -8. 1 7. 2 -6. 1 -4. 6 Change in elon ation (percent) 15. 5 5.4 6. 3 -34.9 -32. 7 Change in 1 o modulus (percent) 17.4 --9. 7 -7.0 +6. 1 +7. 4 Change in hardness -6-7 1-1 -3-4 +3-+2 +6-+B Chan eln volume (percent) +t7.0 +13.1 "+121 +10.B +7.8 Ozone res stance, 100 p.p.m.,

elongation: Number oi hours passed before first crack appeared 1. 0 1. 5 9

1 Measured with products at 155 0., 46 minutes vuleanizatiemaccordlng to ASTM D-3D5-6t.

1 Measured in accordance with ASTM D-39-i-59. 1 No crack observed.

As can be understood from comparing the examples of this invention with the controls, the vulcanized products of NBR-CHR blended compositions in accordance with the invention show synergistically improved strength ,3, The covulcanizable composition of claim 1 wherein said butadiene acrylonitrile copolymer rubber has a Mooney viscosity, ML C.), of 30-130 and said epichlorohydrin polymer rubber has a Mooney viscosity, ML (100 C.), of 40-140.

References Cited ,UNITED STATES PATENTS 3,102,102 8/1963 'Wcidner et a1 260-887 3,278,457 10/1966 Milgrom 260-887 3,285,804 Ill-1966 Robinson 260-887 3,310,523 3/1967 Lenas 260-887 3,351,517 11/1967 Willis 260-887 JOHN C. BLEUTGE, Primary Examiner US. Cl. X.R.

26 0-37 AL, 41.5 R, 887

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,639,651 Da ed February 1, 1972v Inventor(s) KOMURO ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 2, in Table 2, the 14th entry under the heading Control 2,

delete "-19.3" and insert -l9.4

Page 2, in Table 2, the 15th entry under the heading Control 2,

delete "-2.4" and insert -2.3

Page 2, in Table 2-, the l7th entry under the heading Control 2,

insert .4 after 9". n

Page 2, in Table 2, the 18th entry under the heading Control 2,

' delete ".4".

Page 3, in Table 4, the 4th entry under the heading Example 4,

delete "57 -5l" and insert" 59-51 Page 4, in Table 8, delete "3" before the word "Control".

Signed and sealed this 13th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERI'GOTTSCHALK Attesting Officer Commissioner of Patents FORM po'wso (m'sgl USCOMM-DC sous-ps9 U.5. GDVERNMENT PRINTING OFFICE: 1969 0-366-33 

